1. Field of the Invention
The invention concerns closures for containers and more particularly concerns gas-proof, cannula penetrable, self-sealing closures for tubular vacuum holding containers.
2. Brief Description of the Prior Art
The prior art is replete with descriptions of closure members for containers including air evacuated vacuum holding containers; see for example U.S. Pat. Nos. 2,334,905; 3,106,206; 3,136,440; 3,313,439; 3,330,282; 3,460,702; and 3,653,528.
In spite of the highly developed state of the art, closure members for air evacuated containers have many inadequate features and the perfect closure has yet to be developed. For example, in the medical, biological and laboratory fields, sealed vacuum holding tubular containers are frequently provided having cannula pierceable, self-sealing, elastomeric, gas-proof closures whereby entry into the container may be obtained by means of a needle so that fluids may be inserted or withdrawn without breaking the sterility of the container. After the needle is removed from the closure, the closure immediately reseals the pierced entry. One type of closure member frequently used with air evacuated containers is an elastomeric plug having an enlarged head portion and recesses in upper and lower portions to provide a cannula penetrable zone; see for example FIG. 4 of U.S. Pats. Nos. 3,136,440 and 3,106,206. In general, the prior art closure members for vacuum holding tubular containers are relatively thick, relatively inflexible and require relatively high forces for insertion in the open end of an air evacuated tubular container.
The closure member of my invention is an improvement over the prior art closures in that it requires less material (about 30% by weight less) for construction, without a sacrifice of gas-proofing or vacuum holding capacity. Having less bulk and lighter construction, the closure member of my invention is less costly to produce, is easier to assemble in the air evacuated container and requires a much lower force to penetrate with a needle. The latter is particularly advantageous to a more efficient utilization of the container assembly by the consumer.
The structure of my novel closure member also provides for a novel method of inserting an elastomeric closure into an air evacuated tubular container. Prior hereto, such assembly has required considerable force to make the insertion. By the method of my invention, less force is required to insert and assemble the closure member of an air evacuated tubular container. This of course is advantageous in that there is less hazard and a reduction in breakage.